dolfin team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

On 31 August 2011 22:03, Anders Logg <logg@xxxxxxxxx> wrote:
> On Wed, Aug 31, 2011 at 09:20:22PM +0200, Martin Sandve Alnæs wrote:
>> On 31 August 2011 21:13, Anders Logg <logg@xxxxxxxxx> wrote:
>> > On Wed, Aug 31, 2011 at 09:10:21PM +0200, Martin Sandve Alnæs wrote:
>> >> On 31 August 2011 16:12, Anders Logg <logg@xxxxxxxxx> wrote:
>> >> > I want to declare the following function:
>> >> >
>> >> >  template<class S, class T>
>> >> >  void apply_markers(S<T>& sub_domains, T sub_domain) const;
>> >> >
>> >> > S is a template class (either MeshFunction or MeshMarkers) and T is a
>> >> > primitive type.
>> >> >
>> >> > The above declaration does not work. How should it be declared? I've
>> >> > tried various other combinations without success.
>> >>
>> >>
>> >> If you can make T a typedef in S, this works:
>> >>
>> >>
>> >> template<typename V>
>> >> class Foo
>> >> {
>> >> public:
>> >>     typedef V value_type;
>> >> };
>> >>
>> >> template<typename S>
>> >> void apply_markers(S & sub_domains, typename S::value_type sub_domain)
>> >> {
>> >>   S s;
>> >> }
>> >>
>> >> int main(int argc, char *argv[])
>> >> {
>> >>     Foo<int> a;
>> >>     apply_markers< Foo<int> >(a, 3);
>> >>     return 0;
>> >> }
>> >
>> > Thanks. I think I just found another solution (remains to be seen,
>> > currently compiling...). I simply do
>> >
>> > template<class S, class T>
>> > void apply_markers(S& sub_domains, T sub_domain) const;
>> >
>> > S happens to be a template type over T, but it's not necessary to
>> > write that out explicitly in the above function definition.
>>
>> Adding something like "typedef T value_type;" in S makes
>> this more explicit, and is the standard approach in stl and boost.
>
> So we should have this in all our container template classes?
> (MeshFunction, Array, MeshMarkers, maybe others)

A consistent convention like that may make some template stuff smoother, yes.

Martin